A gas generator is required to steadily operate even after the gas generator is continuously mounted on a vehicle for a long period under a severe temperature condition. To cope with various environmental changes, the gas generator is required to unfailingly ignite a gas generating agent therein and exhibit predetermined performance even under an extreme temperature condition at −45° C. to +85° C.
Therefore, it is important for the gas generator to surely carry out the ignition of the gas generating agent at an initial stage of the operation of the gas generator.
It is known that the gas generating agent thermally decomposes when it is exposed to high temperature under the presence of moisture. Therefore, as disclosed in JP-B No. 4703837 (JP-A No. 2001-213688), JP-A No. H11-343191, and WO-A No. 99/54270, zeolite is used to increase heat resistance of the gas generating agent.
On the other hand, recently, a gas generating agent having a low combustion temperature is used. This is because, if the combustion temperature can be lowered, it is possible to reduce an amount of use of a coolant/filter necessary for the gas generator and reduce the size and the weight of the gas generator.
As such a gas generating agent, a gas generating agent including basic metal nitrate disclosed in JP-A No. H09-328389 is used.